Optopatch: high-throughput all-optical electrophysiology for neural recording The convergence of stem cell, genomic, and advanced imaging technologies provides unprecedented ability to study human neural physiology, in health and disease. Traditionally intractable diseases-schizophrenia, autism, Alzheimer's, ALS and Parkinson's-are being modeled in vitro with stem cell-derived cultures of human neurons. Genome sequencing, and more recently, editing, technologies are helping to disentangle the complex genetic interactions that contribute to the pathophysiology. Yet a key challenge has been to probe neuronal function in stem cell-derived disease models with single-cell resolution, adequate throughput, and over repeated measurements. Due to its low throughput, manual electrophysiology is not compatible with drug screening. Direct visualization of neural activity-conversion of action potentials into flashes of light- would revolutionize our study of neural circuits. The Cohen Lab has developed a genetic construct that enables simultaneous optical stimulation and optical recording of electrical activity in neurons. One protein converts blue ligh into electrical stimuli; a second protein converts neuronal activity into flashes of near infrared fluorescence. Q-State Biosciences aims to develop the technology to take this tool from the lab to the marketplace. The aim of this proposal is to develop a prototype instrument for simultaneous spatially resolved optical stimulation and imaging (Optopatch) in complex neuronal cultures. This instrument will enable all-optical electrophysiology in samples containing up to 2,000 neurons, with millisecond temporal resolution, micron spatial resolution, and independent stimulation and readout of each cell. The Cohen Lab has a proof-of-principle machine with these capabilities. Many neuroscience, cardiology, stem cell, and pharmaceutical labs would like to use this tool. However, three further advances are needed for the technology to be widely adopted: 1) to create instrumentation which can perform robustly in daily use; 2) to write software to manage and analyze the torrents of high-dimensional data that Optopatch generates; and 3) to develop stimulation analysis protocols that accentuate biologically meaningful features of the neural network, e.g. excitability, synaptic strength, topology, and plasticity.